Camera control system and associated pan/tilt head

ABSTRACT

An apparatus for controlling one or more cameras is provided. The apparatus includes: a mounting sled, a tilt drive motor, a tilt drive train, a pan drive motor, and a pan drive train. The mounting sled includes a camera platform between two sled runners. A lower surface of each sled runner is formed by a circular arc. The tilt drive train includes a tilt drive shaft having an axis perpendicular to the camera platform. The pan drive train includes a pan drive shaft extending along the axis of the tilt drive shaft such that it receives the tilt drive shaft and turns independently and concentrically about the tilt drive shaft. The camera platform receives a camera such that the center of gravity of the camera is aligned with the diameter of the circular arc of the sled runners and the vertical axis of the tilt and pan drive shafts.

This application is a continuation of U.S. patent application Ser. No.12/265,194, filed Nov. 5, 2008, now U.S. Pat. No. 7,811,008, which is acontinuation of U.S. patent application Ser. No. 11/122,682, filed May5, 2005, now U.S. Pat. No. 7,527,439, titled “CAMERA CONTROL SYSTEM ANDASSOCIATED PAN/TILT HEAD,” which claims the priority benefit of U.S.Provisional Application Ser. No. 60/568,596, filed May 6, 2004, thedisclosures of which are incorporated herein by reference in theirentirety.

BACKGROUND OF INVENTION

The invention relates to a control system for a camera. It findsparticular application in conjunction with a pan/tilt head andassociated methods for controlling one or more cameras and will bedescribed with particular reference thereto. However, it is to beappreciated that the invention is also amenable to other applications.For example, the pan/tilt head may be used to control another type ofpayload instead of a camera payload.

In the design of any camera control system, an important factor to beconsidered is the camera's center of gravity (c.g.). The farther thecamera's c.g. is from either motion axis (such as motion around thevertical axis, otherwise known as “pan” or motion around the horizontalaxis, otherwise known as “tilt”) the more torque will be needed to movethe camera to the desired location. Historically, designers of remotecontrol pan/tilt camera heads have dealt with the issue of camera c.g.in one of two ways.

In one approach, previous designers chose one or the other (vertical orhorizontal) axis and rotated the camera around its c.g. in that axisonly. If the designers choose to rotate the camera around the verticalaxis, then the camera is mounted on the top of the device. The problemwith this design is that as soon as the camera is tilted or moved aroundthe horizontal axis, the weight of the camera is shifted forward orbackward. This weight must then be lifted in order to revert to theoriginal position and, until that is done, the whole system of cameraand mount is in an unbalanced state. This imbalance requires more motorforce to move the camera. If the designers choose to rotate the cameraaround the horizontal axis, then the camera is mounted from the side ofthe device. Here, the camera may be tilted up and down without shiftingits weight forward and backward, but additional torque is required topan the camera since the c.g. of the camera is offset from the center ofrotation around the vertical axis.

In other approaches, previous designs feature the camera moving bothhorizontally and vertically around the camera's c.g. This is done usinga relatively large framework and an “L-shaped” or “U-shaped” bracket.The tilting motor and bearings are located to the side of the camera,and the panning motor and bearings are located directly below (or above)the camera. Though the camera usually remains balanced, it is at theexpense of a larger and heavier support framework, which must be movedright along with the camera as it is panned.

The concept of a circular sled or cam design has existed for many yearsin the design of traditional pan/tilt heads for cameras in the filmindustry because of the requirements of large and heavy film cameras. Inprevious designs, the sled moves independently from the main chassisbody with respect to vertical tilting around the horizontal axis, but itdoes not do so with respect to the panning motion. Previously,horizontal panning was initiated at the base of the entire chassisrequiring that the entire assembly (camera and pan/tilt head) be movedfrom left to right. This is also the case with the prior camera mountconfigurations described above. In previous designs, the camera and itsmounting plate are not isolated from the motor chassis and supportingframework with respect to motion around both the vertical and horizontalaxes.

In previous motorized pan/tilt head designs, the path of thetransmission of power from the motor to the camera mounting structure isalong a different axis for movement in the horizontal and verticalplanes. Therefore movement around one axis changes the positionalrelationship and the contact point between the camera mounting structureand the motor for movement around the other axis. In prior remotecontrol pan/tilt head designs, the solution invariably chosen involvedisolating the camera mounting bracket from the motor chassis andstructural framework with respect to movement around the horizontal axis(tilting) while locking the camera mounting bracket to the motor chassiswith respect to movement around the vertical axis (panning). In otherwords, when tilting, only the camera and mounting bracket moves, butwhen panning, the entire device, including both motors, is moved. Thisincreases the torque requirement of the panning motor significantly. Themain body of the pan/tilt head, as well as both pan and tilt motors,remain stationary as the camera and its mounting apparatus move aroundboth the horizontal and vertical axes.

In the past, the bottom surfaces of circular sled runners have had aflat cross-section enabling it to roll smoothly over the flat races ofeither ball or roller bearings. Of course, free movement forward andbackward over the bearings is necessary, but side to side play isundesirable.

Methods for controlling any remote control pan/tilt head have typicallyfallen into three categories. Most common is the “joystick” method ofcontrol. As the operator pushes a switched lever either left, right, upor down, the camera moves likewise. The problem with this method is thatit is not natural for a trained camera operator. It is difficult to makegentle or subtle moves because there is no sensory feedback to your handwhich signals how the camera is responding. The resultant movesinvariably look very mechanical and unnatural. The second method employsa computer interface to convert either pressure on a pressure sensitivetablet or touch sensitive screen into commands for the remote controlcamera head. Though with practice, this is probably preferable to ajoystick, it still does not provide enough feedback or information tothe user to make lifelike camera moves. The third method uses anelectromechanical control arm identical in size and feel to the arm on atraditional mechanical pan/tilt head. Currently, this type ofelectromechanical control arm has been implemented using a traditionalmechanical panning head at its center. Two position encoders (one foreach axis of movement) are added to this head. As the operatormanipulates the mechanical pan/tilt head, the computer reads the signalsfrom the encoders that correspond to movements in the controller head.The computer then translates these signals into movement commands forthe remote control head. The camera moves exactly in tandem with thecontrol arm. The distance the controller moves is the distance thecamera moves. The speed the controller is pushed corresponds to thespeed that the camera moves. This offers feedback for smooth “human”camera moves. With a joystick, typically the distance that the lever isdisplaced from its center is proportional to the speed at which thecamera moves. There is no correspondence between the distance thejoystick lever is pushed and the distance the camera moves.

Previous implementations of a computer control interface have offeredlittle more in the way of visual feedback cues than a simple joystick.For example, as you touch a screen or pressure sensitive tablet fartheraway from the center of the control area the camera moves faster in thatdirection. This relies on the operator judging the center of the controlarea as he is concentrating on the picture in his monitor, which can bedifficult. Particular attention is required when the operator wants toslow his camera gradually to a stop. He is required to follow animaginary path back to the center with his finger and if he overshootsthe center point of the control area even slightly, the camera imagewill appear to back up.

Thus, there is a particular need for improvements to existing pan/tiltequipment and methods for controlling one or more cameras in a camerasystem. The invention contemplates a new and improved camera controlsystem with a pan/tilt head that overcomes at least one of theabove-mentioned problems and others.

BRIEF SUMMARY OF INVENTION

In one aspect of the invention, an apparatus for controlling one or morecameras is provided. The apparatus includes: a mounting sled, includinga camera platform disposed between two sled runners, wherein a lowersurface of each sled runner is formed by a circular arc having adetermined diameter, a tilt drive motor, a tilt drive train in operativecommunication with the tilt drive motor and the mounting sled, the tiltdrive train including a tilt drive shaft having an axis extending in aperpendicular direction with respect to the camera platform, whereinoperation of the tilt drive motor moves the mounting sled in a tiltdirection, a pan drive motor, and a pan drive train in operativecommunication with the pan drive motor and the mounting sled, the pandrive train including a pan drive shaft extending in a perpendiculardirection with respect to the camera platform along the axis of the tiltdrive shaft such that the pan drive shaft receives the tilt drive shaftand turns independently and concentrically about the tilt drive shaft,wherein operation of pan drive motor moves the mounting sled in a pandirection. The apparatus is adapted such that when the camera platformreceives a camera the center of gravity of the camera is aligned withthe diameters of the circular arcs of both sled runners along ahorizontal axis and the vertical axis of the tilt and pan drive shafts.

In another embodiment of the invention, the concentric pan and tiltshafts are employed to transmit motion from the pan and tilt motors to adual pantograph camera mounting apparatus. Rather than the circular sledor cam mount, the camera platform is supported at the corners by fourvertical bars that elevate and rotate the camera platform such that thecamera moves around its center of gravity in both the vertical andhorizontal axes. The vertical support bars are constrained to verticalorientation by the dual pantographic linkages by which they are attachedto the chassis of the invention and driven by the pan and tilt motors.

Benefits and advantages of the invention will become apparent to thoseof ordinary skill in the art upon reading and understanding thedescription of the invention provided herein.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in more detail in conjunction with a set ofaccompanying drawings.

FIG. 1 is an embodiment of a pan/tilt head with a 90-degree cutawayform.

FIG. 2 is another view of the pan/tilt head of FIG. 1 with a differentcutaway form

FIG. 3 is another embodiment of a pan/tilt head.

FIG. 4 is yet another embodiment of a pan/tilt head with a displaymonitor installed thereon.

FIG. 5 is another view of the pan/tilt head of FIG. 4 with a videocamera installed thereon.

FIG. 6 shows an exemplary computer display during operation of thecamera control system.

FIG. 7 shows another exemplary computer display during operation of thecamera control system.

FIG. 8 shows yet another exemplary computer display during operation ofthe camera control system.

FIG. 9 shows still another exemplary computer display during operationof the camera control system.

FIG. 10 is still another embodiment of a pan/tilt head.

FIG. 11 shows a cross sectional view of an embodiment of a sled runnerassociated with a pan/tilt head.

FIG. 12 shows a cutaway view of another embodiment employing theframeless torque motors and a pantographic mounting apparatus.

FIG. 13 shows a graphic representation of the dual pantograph linkage.

FIG. 14 shows the pantograph linkage having been tilted 30 degrees.

FIG. 15 shows the cable drive train used in conjunction with thepantographic mounting apparatus.

FIG. 16 shows the pantographic linkage used with the tilt motor rotated90 degrees.

FIG. 17 is a graph depicting a large maximum drag over a wide range ofPPC/APC differential values.

FIG. 18 is a graph depicting a small maximum drag over a small range ofPPC/APC differential values.

FIG. 19 is a graph where the drag is constant and independent of speedexcept for the spike of force required to initiate any movement.

FIG. 20 is a graph in which the drag increases as the speed increases.

FIG. 21 is a graph in which the drag decreases as the speed increases.

DETAILED DESCRIPTION

While the invention is described in conjunction with the accompanyingdrawings, the drawings are for purposes of illustrating exemplaryembodiments of the invention and are not to be construed as limiting theinvention to such embodiments. It is understood that the invention maytake form in various components and arrangement of components and invarious steps and arrangement of steps beyond those provided in thedrawings and associated description. Within the drawings, like referencenumerals denote like elements.

The camera control system is comprised of several discrete components,which combine to provide camera control while giving specialconsideration to the parameters of camera payload weight, speed ofmovement, physical size, visual obtrusiveness, audible noise,adaptability to different size cameras, and movement consistent withthat of a traditional human-operated mechanical pan/tilt head. In otherwords, an associated pan/tilt head is small, light, quiet, and able tosupport and quickly move a large camera from one position to another ina manner indistinguishable from the traditional manned camera withrespect to the camera's image output. In addition, the inventionaddresses the economic issues of television and film production cost andincreased efficiency and lower cost of operation to the end user. Thesebenefits are made possible by the inclusion of a computer interface,which facilitates a limited number of technicians operating a largenumber of cameras.

In one aspect of the invention, the pan/tilt head moves the cameraaround its c.g. with respect to both the vertical and horizontal axis.It does so, however, while maintaining a smaller more compact framework,which is situated directly below the camera. In an alternateconfiguration, the unit may be operated in an inverted position wherethe camera is suspended beneath the mount. In one embodiment of thepan/tilt head, the camera is mounted on a movable “sled” with circularrunners, which travel on fixed roller bearings. As the sled rolls on itsrunners over the bearings, the camera is tilted up and down. Because thec.g. of the camera is positioned exactly at the center of the virtualcircle described by the arc of the sled runners, it is not shiftedeither forward, backward, up, or down. The camera is also mounted withits c.g. directly on the vertical axis, so panning the camera left andright requires minimum motor torque.

FIG. 1 depicts one embodiment of the pan/tilt head incorporating aspectsof the invention with a 90-degree cutaway form. The vertex of thecutaway represents the center of the power transmission shafts for boththe panning and tilting axis. The pan/tilt head includes a tilt motor10, a worm screw 11, a worm gear 12, a tilt drive shaft 13, a pan motor14, a worm screw 15, a worm gear 16, a pan drive shaft 17, a pan drivebelt 18, a pulley 19, a tilt drive belt 20, and a pulley 21. Thesecomponents form separate pan and tilt drive trains. The camera isaffixed to the mounting sled, which is composed of a camera platform 22and two sled runners 23. Supporting the mounting sled is a sled support,which is composed of a sled support table 24 and two sled support sides25. Finally, the pan and tilt drive shafts are supported and allowed torotate freely by a series of four bearing units. There are two pan driveshaft bearings 26 and two tilt drive shaft bearings 27.

The configuration of the tilt drive train depicted in FIG. 1 is chosenfor its strength when heavier loads are to be carried by the cameraplatform 22. Of course, any one or more of the various screws, gears,shafts, belts, and pulleys making up the tilt drive train may bereplaced by one or more drive train components capable of accomplishinglike or similar functions. For example, FIG. 10 shows many of the drivetrain components above the motor housing case top 28 replaced withseveral pulleys 32, 33, 34 and a cable 35.

In FIG. 10, the pan/tilt head includes the tilt motor 10, the worm screw11, the worm gear 12, and the tilt drive shaft 13. A first pulley 32 isdisposed at an end of the tilt drive shaft 13 extending through themotor housing case top 28 toward the camera platform 22. Second andthird pulleys 33, 34 are disposed at opposing corners of the sledsupport table 24. Ends of the tilt drive cable 35 are secured toopposite sled runners 23 at points near where the sled runner 23 meetsthe camera platform 22 and opposite from ends of the sled runner 23adjacent to the second or third pulley 33,34. Note that in theembodiment depicted in FIG. 10, a groove 36 is formed in the bottomsurface of both sled runners 23. The groove 36 is shown in more detailin a vertical cross section of the sled runner 23 taken parallel to thetilt axis (FIG. 11).

The drive cable 35 is wrapped around the first pulley 32, which acts asthe main drive pulley, routed around the second and third pulleys 33,34, which act as guide pulleys, and routed along the grooves 36 in thebottom surface of the sled runners 23 to the points at which it issecured. The drive cable 35 is tensioned so that, when the tilt motor 10turns in one direction, a corresponding end of the sled is pulleddownward and, when the tilt motor 10 turns in the opposite direction,the opposite end of the sled is pulled downward. In this way, rotationof the first pulley 32 pulls the edges of one or the other sled sidestoward the bottom of its rotation path, thus initiating the tilt motion.Although the embodiment with the cable may have less strength inheavy-duty applications, it has the advantage of greater accuracy, lessbacklash and fewer parts than the embodiment shown in FIGS. 1-3.

The invention incorporates the concept of motion in both pan and tiltaxes around the camera c.g. in combination other special features in theareas of remote control and power-assisted control.

In the invention, the camera mounting structure (consisting of thecamera platform 22 and runners 23 and sled support table 24 and sides25) is isolated from the motor chassis with respect to both the panningand tilting motions. This is to say that both motors and their housingremain stationary during both pan and tilt movement. This isaccomplished by using a bearing and shaft assembly which transmits thedriving force of both the panning and tilting motors to the mountingsled along the same axial line. The pan drive shaft 17 which transmitsthe power from the panning motor to the sled assembly is hollow and actsas the housing for the tilt drive shaft bearings 27 and tilt drive shaft13 which transmits the power from the tilting motor to the sledassembly. In the embodiment pictured in FIG. 1, the sled support table24 is bolted rigidly to a flange at the top of the hollow pan driveshaft 17. A motor housing case top 28 acts as the support structure forthe outer races of both of the pan drive shaft bearing units 26. Theouter edge of the flange of the pan drive shaft 17 and a hexagonallocking ring 29 are the supports for the inner races of both of the pandrive shaft bearing units 26.

FIG. 2 is another view of the pan/tilt head shown in FIG. 1 with acutaway view through the camera platform 22 and runners 23 and the sledsupport table 24 and sled support sides 25. This view also depicts acutaway view of two sled mounting roller bearings 30 and 31.

The embodiment of the pan/tilt head being described solves the problemof lateral movement of the mounting sled by shaping the bottom surfaceof one or both of the runners to form a point with respect to the crosssection of the bottom of the runner. See the runner cross section inFIG. 11. The two surfaces that form the point fit securely into av-grooved roller 29 rather than a flat roller bearing race. In oneembodiment (FIGS. 1-3), the v-groove roller is on one side. This limitsoverall lateral movement without imposing reduced tolerances to ensurethe sled does not bind between v-groove rollers on both sides should thesides of the sled become not parallel at some point for some reason.Nevertheless, the v-groove rollers 29 and sled runners 23 may beconstructed with sufficient tolerances to permit both runners to havepointed bottom surfaces in another embodiment (FIG. 10). The two sledrunners are held in contact with races (e.g., flat on one side andv-grooved on the other) by an additional set of bearings which rideagainst a lip formed on the inside edge of the sled runners. Because ofthe additional set of bearings on the inside of the runners holding themagainst the external bearings, and because of the v-groove pulleys,unwanted movement of the mounting sled in all directions is limited andminimized. This configuration also allows the unit to be operated in aninverted position.

Another embodiment of the invention features a camera mountconfiguration which offers the same advantage of under-camera mountingand movement around the camera c.g. in both axes while allowingadjustment for cameras of different height. The sled or cam designpreviously described involves fewer moving parts, but must beconstructed with a sled diameter chosen for a specific height of camera,(although the weight of the payload is irrelevant.). FIG. 12 depictsthis embodiment of the pan/tilt head incorporating aspects of theinvention with a 90-degree cutaway form. The pan/tilt head includes apan motor stator 40 and rotor 41, a tilt motor stator 42 and rotor 43,an upper elevator arm 44 and lower elevator arm 45 on each side, anupper crossbar 46 and lower crossbar 47 on each side, a pan table 48,with two pan table sides 49, a camera platform 50, a pan shaft 51, atilt shaft 52, eight elevator arm bearings 53, eight crossbar bearings54, a pan shaft position encoder 55, a tilt shaft position encoder 56,four vertical support bars 57, two pan shaft bearings 58, two tilt shaftbearings 59, a tilt shaft drive pulley 60, two cable guide pulleys 61and two elevator arm pulleys 62.

This embodiment uses a dual pantograph linkage instead of the sled camto transmit the power from the pan table to the camera-mountingplatform. Two elevator arms 44, 45, on each side of the pan/tilt headare connected to the pan-table sides 49 and allowed to rotate around thecenters of the upper and lower elevator arm bearings 53. A crossbar 46is attached to each of the elevator arms in a manner, such as slottedholes and corresponding bolts, which allows the effective length of theelevator arms to be adjusted. At the left and right extremities of thecrossbars, there are bearings 54 connecting each vertical cameraplatform support (vertical support) 57 with one end of the upper andlower crossbar 46, 47. There are four vertical supports in totalsupporting the camera platform 50 at each of its four corners. Theeffective length of each elevator arm is the distance from the center ofthe pan-table side bearing to the perpendicular line described by thebearings at the ends of its crossbar. This linkage configuration can bethought of as a dual pantograph because of the two parallelograms formedon each side of the pan-tilt head by the pan-table side 49, the frontand rear vertical supports 57 on either side of it, and the imaginarylines between the elevator arm bearings 53 and the crossbar bearings 54.It should be noted that for free movement in the tilting plane, thedistance between the upper and lower crossbar bearings where they attacheach crossbar to the vertical support is the same as the distancebetween the upper and lower elevator arm bearings.

FIG. 13 shows a graphical representation of the relationship between theelevator arm bearings (A and B), the crossbar bearings, (D and E), thevertical supports (line YDE), and the camera platform (dashed line XY).The dashed line descending from point B represents the effective lengthof the elevator arms. This length should be adjusted so that it is thesame as the dashed line descending from point C, which represents theheight from the base of the camera to the camera c.g. and the center ofthe dashed circle. The dashed circle in FIG. 13 represents therevolution of the camera platform and its radius is the same as thedistance from elevator arm bearing A to crossbar bearing D (line AD).

In FIG. 14 the elevator arms have been rotated 30 degrees around theirbearings (points A″ and B′). In the invention, the bearings at points Aand D are fixed with respect to the rotating pan-table. Because of thepantograph action of the elevator arms and crossbars, the verticalsupports are held upright and parallel to the line formed by the upperand lower side bearings (line Y′D′E′). As the vertical supports travelalong an arc following the circumference of the dashed circle, theconnected camera platform and attached camera are tilted, followingalong the same arc depicted by the dashed circle. It can be seen thatthroughout this motion the camera c.g. at point C remains fixed directlyabove the centerline marked by the elevator arm bearings A and B (lineAB).

FIG. 15 depicts the cable drive train used in the dual pantographembodiment. In this case, instead of the sled side, the cable is fixedto an elevator arm pulley 62 on each side of the pan-table and travelsback over the guide pulleys 61 to the tilt shaft pulley 60. Rotation ofthe tilt motor 42 is transmitted through the tilt drive shaft 52 to thetilt shaft pulley 60 where it is again transmitted through the cable tothe two elevator arm pulleys 62.

The invention offers significant advantages to the film or televisionproducer over other pan/tilt heads, including remote pan/tilt heads.Remote control cameras are often used because of particular constraintsthat make a traditional manned camera difficult to employ. For example,a camera placed inside a moving racecar, where there is very limitedavailable space. The invention allows for a much more compact panninghead for a given camera weight. Since both motors transmit their poweralong the same axis, they may be mounted side by side in a much smallerenclosure than another remote control head where the two motors need tobe somewhat removed from each other and positioned along axes which aredisplaced by 90 degrees from each other. Because the motors do not needto move their own weight as well as that of the camera, a less powerfuland quieter motor may be used for a given camera weight. Less audiblenoise is desirable, for example, to the producer of a musical ortheatrical event where an audience is present.

FIG. 12 depicts an embodiment of the invention that employs a motorconfiguration that takes particular advantage of the concentricpositioning of the pan and tilt drive shafts. In a case where highercamera rotation speeds are required (and a reduced positioningaccuracy), frameless torque motors may be employed in a direct driveconfiguration. Each motor is manufactured in two pieces—a rotor 41 and astator 42. These motors do not have the housing and shaft bearings seenin most motors. In this case, the housing for the pan/tilt head providesthe covering for each of two motor stators and rotors. The rotors arehollow. One rotor is fixed rigidly to the pan shaft 51 and the otherrotor to the tilt shaft 52. The same bearings 58, 59, that support eachof the pan and tilt shafts support the motor rotors and allow them toturn as an electric field is produced in the surrounding motor windings.This configuration allows for a cylindrical motor chassis (when viewedfrom above) which allows for better clearance for the camera rotatingabove. It is also potentially faster because speed reducing gears arenot necessarily needed between the motor shaft and the associated pan ortilt shaft. However, as noted above, since the motor and, therefore, therotation position encoder attached to it do, not make multiplerevolutions for each camera revolution, the potential positioningresolution is reduced for a given encoder.

FIG. 16 depicts another embodiment of the invention that combinesfeatures described above in another way in order to offer a unique setof advantages in certain circumstances. Previous embodiments haveemployed the concentrically mounted motors and drive shafts in order tominimize the mass of the moving parts. In some cases it may also be seenas advantageous for the pan tilt head to project the basic footprint andpossess more of the basic appearance of the traditional mechanicalpan-tilt head. In this embodiment a pan motor 14′ has been rotated 90degrees while a tilt motor 10′ has retained its horizontal orientation.In other words, the pan motor is mounted so that its drive shaft turnsin a vertical axis, while the tilt motor is mounted (as previouslydescribed) so that its drive shaft turns in a horizontal axis. In thisembodiment, not only does the entire apparatus have a more traditionalappearance, but, by placing the tilt motor 10′ between the pantographiclinkages 46, 47, 57 as shown in FIG. 16, the tilt drive shaft may now bedriven directly without the use of the tilt drive pulleys and cable. Forexample, in the embodiment with the pantographic linkage 46, 47, 57, thetilt drive shaft 13′ (shown in phantom in FIG. 16) extends through thetwo bearings of the lower elevator arms 47 and runs directly through thecenter of the tilt motor 10′. The rotor of the frameless tilt motor ismounted on the tilt drive shaft 13′ and relies on the elevator armbearings for support during its rotation. All other aspects of the dualpantograph mounting remain the same as previously described.

In several embodiments, the invention offers two types of control. Onetype of control, which may be less expensive, provides remote controlvia a computer interface. Another type of control providespower-assisted control via an electromechanical control arm.Power-assisted control maintains a high degree of control feedback andsensitivity and may be implemented for remote control or for localoperator control of a manned camera.

The computer interface in one embodiment of the invention goes fartherthan any system in production or described in the prior art to providethe operator with visual cues for directing cameras on a control screen.As previously stated, this option is provided as a less expensivecontrol method. Typically, a standard computer mouse is used to minimizecost. However, a touch screen or any other type of pointing device maybe implemented.

In the embodiment of the invention being described, the computerinterface provides improved visual feedback cues with features notpreviously disclosed or produced. For example, as the operator positionsthe cursor over the image on the monitor for the camera to becontrolled, a set of lines, one vertical and one horizontal, appearsuperimposed on the picture like “crosshairs.” Any point in the picturemay become the center of motion control depending on where the cursor iswhen the mouse button is depressed. When the button is depressed, thecrosshairs become stationary and further movement (dragging) of thecursor results in the camera image following the cursor up, down, leftand right. Once again, the distance from the movable cursor to thecenter of the crosshairs determines the speed. In addition to thecrosshairs and movable center, several other visual cues are provided tothe operator. As the camera is moved by the cursor, the computerconstantly superimposes a dynamic vector line onto the image from thecamera. This vector line moves as the cursor moves and appears toconnect the cursor and the center-position crosshairs, which weredefined when the mouse button was pressed in the picture area of themonitor. This gives an instantaneous cue to the speed and direction aswell as the path to be followed back to the center for a smooth gradualstop.

Another efficient feature of the computer interface is a graphical aidto zooming and framing. Going back and forth between the zoom controlson the computer keyboard and the motion controls tends not to be asefficient and quick as it is for a manned camera operator. This systemallows you to “drag-enclose” a graphical box directly on the cameraimage. This is done by clicking in the camera image on the computerscreen (with the control key depressed) at the point that you ultimatelywish to be the upper left corner of your composed shot. When you dragthe cursor down and to the right, a box is drawn in the camera imagewhich maintains its correct aspect ratio for the format of the camerabeing controlled (for instance a ratio of 4 by 3 for an NTSC televisionimage.) After the cursor is released, the composition box can either bemoved slightly or its size adjusted to fix the framing. Then the camerais given the command to move to the position and lens zoom setting whichwill fill the camera output image with the image described by thecomposition box originally superimposed on the camera image. FIG. 6depicts the computer screen while the system is being operated. Theupper right window in the screen represents the video control window forthe camera that has been selected for manipulation. This window normallydisplays the actual image from the selected camera over which thecontrol graphics described above is superimposed. FIGS. 7 through 9depict a detail of the video control window during operation. In FIG. 7,the “cross-hairs” are shown positioned slightly to the left and abovethe center of the picture. This becomes the center of movement and isthe point where the cursor is returned in order to smoothly andgradually cease camera movement. FIG. 7 shows the cursor currently beingdragged below and to the right of the center of movement. The vectorline linking the cursor to the crosshairs represents the speed anddirection of the camera movement. In FIG. 8 the resulting position ofthe camera is depicted. Note that the camera is now pointing to aposition that is lower and to the right of FIG. 7. FIG. 8 also depicts azoom framing box. After this box has been drawn by clicking and draggingthe cursor with the appropriate function key depressed, another functionkey will command the camera to move and zoom to the position which willfill the frame with the inscribed picture. The resulting framing for thecamera after the move command is depicted in FIG. 9.

An alternate method of control is the electromechanical positionalcontrol arm. As was stated earlier, in the past this type of controllerwas designed around a traditional pan/tilt head with the addition ofencoders which gave positional information to the remote controlpan/tilt head. The invention takes a different approach. Instead of atraditional panning head at its heart, this controller is comprised of amotorized pan/tilt head similar to the remote control head with acontrol arm attached to the camera mounting sled. In one embodiment,instead of a camera on the camera mounting plate, a video monitor forthe remote controlled camera is situated on the controller's mountingsled. This is depicted in FIG. 4. In this configuration, strain gaugesor pressure sensitive resistors are housed in the handle, which sensethe pressure that the operator applies to the control arm. Instead ofthe hand pressure directly moving the control arm (as is the case withexisting designs) the computer senses the pressure and initiates a movecommand to the control arm motors as well as the identical command tothe remote control camera head. The computer responds to varyingpressure on the control arm with proportionally varied speed commands toboth the control arm motors and the remote control pan/tilt head.Mounting the monitor directly on the panning head in this mannersimulates the feedback that a traditional camera operator has as helooks through the viewfinder of a camera. The movement of the viewfinderand the movement of the camera are integrally locked together so that anexperienced traditional camera operator can quickly begin using thisremote control system without additional training or practice.

One of the features of this embodiment of the invention is that thepressure sensitive control arm can be used on a motorized panning headwith a camera mounted on it instead of the monitor. This configurationthen becomes a power assisted manned pan/tilt head with a camera asdepicted in FIG. 5. This configuration could simultaneously be used bythe camera operator to remotely control other unmanned cameras. Onceagain it should be noted that the hand pressure applied to the handledepicted in FIGS. 4 and 5 does not directly move the camera or monitor.This hand pressure is merely sensed by the microprocessor and translatedinto the pan and tilt motor speed controls. An advantage of this is thatthe pressure sensors in conjunction with the controlling computersoftware could be adjusted to move the heaviest of cameras with theslightest amount of finger pressure if so desired. This offerstremendous flexibility to a television or film producer. With a seriesof these power-assisted pan/tilt heads, each with their own camera andview-finder/monitor, a camera operator could simultaneously operate onecamera with greater ease or control the movement of one or more othercameras in the system.

The embodiment of the invention that employs the frameless torque motorswithout the associated drive gearing, can also be manipulated by handand used directly as a manned pan/tilt head or a controller for otherremote control camera heads. In this embodiment, the strain gauges orpressure sensitive resistors are not needed because the pan and tiltshafts can be moved directly by hand pressure. There is no gearingconnected to the motor rotors to resist this movement when there is noelectricity applied to the motors. Instead of electromagnetic forcedirectly proportional to the hand pressure moving the device, smallamounts of electromagnetic force are used in opposition to the handpressure to give the operator the sense of “drag” which hastraditionally been designed into manned camera heads. In traditionalmechanical pan-tilt heads, the drag or resistance is linear and finemicro adjustment of the drag amount is not possible. With the invention,not only is an extremely wide range of drag possible, but it can bedelineated with a much finer resolution. Also the application of drag isnot merely linear with respect to speed. With the invention, a “dragcurve” can be chosen such that movement at very slow speeds could havemuch less resistance or vice-versa. With traditional mechanical dragdesigns, there is a function of friction in which it takes more force toinitiate movement from the stopped condition than it does to simplycontinue the motion once started. This is also evident when thetraditional pan/tilt head is gradually slowed to a stop. There is apoint where the greater coefficient of stopping friction exceeds thehand force and the camera comes to a small but perceptible abrupt stop.This phenomenon is greatly reduced with the invention. The operator hasa choice about exactly how much drag is desired at any given speed. Thedrag can decrease to zero just as the motion ceases.

In the invention, the microprocessor makes very quick and very smallchanges in the amount of current applied to the motor windings in orderto move the remote control camera at exactly the desired speed. Theacceleration and deceleration are also monitored and adjusted as many as20,000 times per second. This is the same sensitivity that is requiredin order to apply the electromagnetic force in opposition to the handmotion when the invention is used as a locally controlled pan/tilt heador as a controller for a remote head. In the case were themicroprocessor is initiating the movement in the remote control pan/tilthead, a desired position counter (DPC) is maintained within the memoryof the microprocessor which represents the desired position of thatmotor shaft (either pan or tilt) at any moment. The DPC is updatedeither up or down at a frequency corresponding to the desired speed. Anupward incrementing of the DPC would indicate a clockwise rotation.While the incrementing or decrementing of the DPC occurs at fixedintervals, another part of the microprocessor control program isconstantly monitoring the actual position of the pan and tilt shafts asindicated by the optical shaft encoders using an actual position counter(APC). These encoders indicate the direction of the actual movement andgive a short electrical pulse at regular intervals corresponding to afraction of a rotation. The actual position is compared to desiredposition at a given moment and the electrical current to the windings isappropriately adjusted to bring these two measurements together. Inother words, a change is the desired position causes a change in motorcurrent resulting in a change in actual position.

In the case where the invention is being used as a manned camera head orremote camera controller, there is a change in the logic of themicroprocessor. The microprocessor here maintains a “present” positioncounter (PPC) that represents the shaft's “present” rotational position.Any manual pressure on the pan/tilt head control arm will result inrotation of the shaft and optical encoder so that the “actual” positionwill now differ from the PPC. This causes an electromagnetic force to beapplied by the microprocessor in opposition to the manual movement. Asthe difference between the APC and PPC increases so will the opposingmagnetic force. At this point, the magnetic force will increase to thelevel that no further manual motion is possible unless an adjustment ismade to the PPC. When the difference between the APC and PPC reaches alevel predetermined in the microprocessor control program, the PPC isincrementally adjusted in the direction of the APC. Further changes tothe APC will result in changes to the PPC on a one to one basis butmaintaining the predetermined offset. The microprocessor constantlymonitors the offset between the APC and PPC and bases the amount ofopposing electromagnetic force on this factor. As the pan/tilt headcontinues to move in the same direction at a constant speed, drag willremain constant. As the manual force on the control arm is diminished,the speed of the pan/tilt head will decrease as will the differencebetween the APC and the updated PPC. This will result is a decrease inthe electromagnetic drag which will go to zero just as the motion stopsand the PPC is updated to equal the APC. The drag that is apparent tothe operator is dependent on two factors, each of which can be adjustedseveral thousand times per second by the microprocessor depending on thedesired drag curve. First, is the maximum amount of electric currentapplied to the motor windings in opposition to the manual movement.Second, is the distribution of the range of electric current over thepredetermined range in the lag between the actual and present position.Since the lag or difference between the PPC and APC is related to thespeed at which the pan-tilt head is moved, one can express these twofactors in a graph of drag (in units of torque) versus speed. FIG. 17depicts a large maximum drag distributed over a wide range of PPC/APCdifferential values. In effect, at slow speeds the drag is very small,but the drag continues to grow as speed increases until maximum drag isreached. FIG. 18 depicts a small maximum drag distributed over a smallrange of PPC/APC differential values. In effect this is a “constant”drag curve wherein the small maximum drag is attained very quickly, butthen does not increase after that even though movement speed mayincrease. This is the closest to the drag curve of a traditionalmechanical pan/tilt head represented in FIG. 19. In this case the dragis constant and independent of speed except for the spike of forcerequired to initiate any movement. FIGS. 20 and 21 represent otherconceivable practical combinations of different maximum drag current andPPC/APC differential range distributions. Both of these examples showthe nonlinear drag potential of the invention. FIG. 20 depicts a curvein which the drag increases as you attempt to move the pan/tilt headfaster and FIG. 21 is the opposite. It is also possible in some uniquesituations to use the APC by itself (in addition to the PPC/APCdifferential) in the calculation of the drag curve. For instance, inpan/tilt heads there are usually practical limits to the extents oftravel in the pan or tilt axes. This may be caused by mechanical limitsin the apparatus, by the cabling attached to the camera, or by featuresin the landscape, studio, or set where the filming is being done thatare not wanted to be seen in the final product. The invention allows forthe programmable drag to increase as desired pan or tilt limits areapproached, thus providing such feedback to the camera operator andavoiding a hard bump or cable pull from occurring if the limit isreached.

In addition to placing remote controlled cameras in inaccessible ordangerous locations for operators, another desirable feature of a cameracontrol system is that one camera operator can command any number ofcameras. In this embodiment of the invention, the computer softwarehelps an operator manage, organize, and operate multiple cameras. Forinstance, this system may be used in the production of a dramatic ormusical program where a series of preset camera positions preparedbefore the performance is stored and organized in the computer as a “cuelist.” Each preset shot or “cue” is prepared by moving the desiredcamera to the position and lens setting desired by the director. Thecamera is moved by any of the controller options described above. Whenthe command to store the preset is given, the lens settings (whichinclude the focus, iris, and zoom setting) are stored in a databaseentry for each cue or preset along with the pan and tilt position of thecamera mount and the cue number. Each of the shots appear in a computerwindow filled with small thumbnail images representing all of the shotsfrom many different remote control cameras that will be used during theperformance. The cue-list window is shown seen in the left portion ofFIG. 6. The shots appear in the order that they are intended to be usedregardless of which camera is used for each shot. In general,consecutive presets employ different cameras, however if the directorwants to program a dynamic camera move to appear on the program output,this is represented in the cue list by consecutive presets for the samecamera. The two presets represent the starting and ending point for thatprogrammed camera move. In this case, information is stored in the cuelist database to represent the speed at which the camera should movefrom its starting to its ending position.

At the beginning of the program, all of the cameras are positioned totheir respective initial presets. At that point, all the operator needdo is hit the “return” key when each successive shot is needed. Thecomputer then triggers a video mixer to make the programmed transitionfrom one camera to another on the main program. It is this video mixerwhich routes the desired camera output either to broadcast air, videotape recorder, or a projection monitor where it will ultimately be seenby the audience. When the video mixer transitions from one camera toanother, the camera which was previously seen, is now free to be movedby the computer to the next position in which it will be used in the cuelist. In addition to the preprogrammed camera moves described above, aremote camera operator could override computer control at any moment andmove any of the cameras including the “on air” camera if he so desires.Also, in a situation between that of total manual override and totalcomputer control, the computer still maintains the order of shotsrequired by the programmed cue list. The computer automatically providesthe remote control camera operator with control of the specific camerathat is appearing on the air at that moment. This frees the operatorfrom keeping track of which camera was required for which shot and inwhich order. In addition, control of the preview camera (the camera thatis designated to be seen next) could be routed to a remote controlcamera operator to make any adjustments to the camera that are neededbefore the camera appears “on air.” In this way, two or three peoplecould competently manage a production involving a large number ofcameras.

The system offers several features for managing several remote controlcameras in a production that is not entirely scripted, such as asporting event. Several preprogrammed shots for each camera appear inthe computer control window sorted by camera number rather than anumbered cue list. The director could quickly select a shot by clickingthat shot's thumbnail image and the designated camera is instantly sentto that position.

One of the features of the computer interface is the ability tocalculate the position of a subject in three-dimensional space from theposition of two and in some cases one camera trained on that subject. Ifone remote control camera is placed at a sufficient and known heightabove a plane such as a stage, studio or playing field, the computercalculates the position of a subject on that known plane based on thepan and tilt positions of that elevated camera. The computer must begiven the height of the camera above the stage or field, and then as thecamera operator moves the master camera to follow the subject, theposition of the subject on that stage or field may be calculated usingthe following formulae:D=H*tan(90−t)AndL=D*tan(p)Where

D=depth or distance of subject to vertical line of camera position

L=lateral displacement of subject from center line of stage or field

t=the tilt angle from horizontal

p=the pan angle from the center line of the stage

Using similar formulae, the computer may then direct any of the otherremote control cameras in the system to the previously calculatedsubject position. The computer needs the pan and tilt angle and thedistance from the original master positioning camera located above theplane of the stage or field to any other desired slave camera in thesystem to do so. The pan and tilt angles may be derived from simplysighting the slave remote control camera in the center of the field ofview of the master positioning camera. The distances between each of thecameras and the subject are also calculated for the purpose of focusingeach of the camera lenses automatically. If it is not possible toelevate one camera above the subjects, two remote control cameras in thesystem may be focused on a subject from different locations. When thecomputer is given the accurate distance between the two locator camerapositions, the system is able to focus all the other remote controlcameras in the system on a subject based on the triangle formed by thetwo locator cameras and their respective pan and tilt positions.

The embodiment of the remote control pan/tilt head described aboveallows for several production configurations that include pan/tilt headsfrom earlier designs. Because the camera mounting structure is isolatedfrom both the pan and tilt motors, the shafts can be elongated to thepoint where the mounting sled can be situated far above the actualmotors driving the sled. This can be seen in FIG. 3, which shows theinvention with extended pan and tilt drive shafts. This allows a supportto house the motors near the floor where their weight adds to thestability of the stand rather than positioning them at the top of thestand which needs to be stiffer and heavier as a result. This alsoresults in a smaller visual profile exposed to a studio or live audiencethat may find a larger camera control configuration more visuallyintrusive. FIG. 3 does not depict all of the support structures whichare required for the operation of this or any remote control system, butshows the main parts of the invention which could be incorporated into astand or mount to gain the benefits mentioned in this paragraph.

Another embodiment of the invention is its use with a camera “crane” or“camera jib arm.” This is an apparatus that holds a camera out at theend of what may be a very long extension arm. The arm is generally toolong to be reached by the camera operator so the camera must be moved bysome manner of remote control. The most common way to control the cameraat the end of the crane arm is mechanically. In this method, a cameradirection control rod is mounted beside the main crane arm to form apantograph system. In this way, as the main crane arm is moved, thecamera always remains directed along a line that is parallel to itsoriginal position. Another pantograph arm can be situated beneath themain crane arm so that as the crane is lifted up and down, the cameraretains its original tilt angle with respect to the ground or floor.This invention accomplishes the remote control of the cameraelectromechanically.

The computer control system in this invention makes certain controloptions available which have not been present in previous systems. Withthe purely mechanical system, the advantage is that when the main cranearm is elevated or rotated, the camera maintains its directionalorientation without attention from the camera operator. The disadvantageis that the subject is usually close enough to the crane that as thecrane arm is manipulated, small adjustments to the camera direction needto be made to keep the subject framed in the camera image. With anelectromechanical remote control pan/tilt head as well, the operator ofthe crane is obliged to manipulate the camera pan/tilt controls as he ismoving the crane in order to keep the subject framed in the cameraimage.

With the invention, the camera/crane operator can be freed of many ofthe control requirements by the computer control system. In thisembodiment of the invention, the remote control pan/tilt head can besituated on the end of a crane that has been outfitted with two rotationencoders at the fulcrum of the crane. By reading the output of theseencoders, the computer senses the orientation of the crane arm andadjust the pan/tilt head accordingly. As the crane is elevated orrotated, the computer could be set to respond in one of several modes.In one mode, the computer could keep the camera oriented in a line thatis parallel to its position before the crane arm was moved. This isanalogous to the situation with the mechanically controlled crane.

In another mode, the computer allows the operator directional control ofthe pan/tilt head just as any remote control head for cameras has donein the past. In another mode the operator has the unique ability toinput the distance from the crane to the subject. At this point thecomputer is able to automatically keep the subject framed within theimage frame without any additional input from the operator as the cranearm was manipulated. In yet another mode, the camera/crane operator isresponsible for keeping the subject in focus by manipulating the remotefocus controls of the invention. The computer calculates the distance tothe subject from the focal length of the lens. Then once again, as inthe previous mode, the computer could keep the subject framed in thecamera image regardless of the crane arm orientation.

In summary, various aspects of the camera control system in variousembodiments have been described herein. For example, in one aspect, thedual shaft drive in the pan/tilt head allows the camera to moveindependently from the motor chassis. In another aspect, the computerinterface offers graphical assistance to the operator while providing alow cost control option. In yet another aspect, the addition of anelectromechanical control arm to the pan/tilt head serves as anintuitive natural controller for a remote control camera. I have alsodiscussed an embodiment that places a camera directly on top of thispan/tilt head/control arm combination to provide “power assisted”control of a manned camera head. Given the tremendous cost involved inproducing a traditional camera head that can easily support and move thelargest film and studio cameras with minimal operator force, this is avaluable aspect of the invention. Still another aspect of the inventioninvolves the use of the pan/tilt head on an extended crane or “jib arm,”with computer-assisted positioning of the pan/tilt head as the crane isrotated or elevated.

While the invention is described herein in conjunction with exemplaryembodiments, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. Accordingly,the embodiments of the invention in the preceding description areintended to be illustrative, rather than limiting, of the spirit andscope of the invention. More specifically, it is intended that theinvention embrace all alternatives, modifications, and variations of theexemplary embodiments described herein that fall within the spirit andscope of the appended claims or the equivalents thereof.

1. A pan/tilt head comprising: a mounting platform; a pan table locatedbeneath the mounting platform; and a first pantograph linkage connectedto the mounting platform and to the pan table, the pantograph linkageconfigured to permit the mounting platform to tilt with respect to thepan table without moving a center-of-gravity defined respective to themounting platform.
 2. The pan/tilt head as set forth in claim 1, whereinthe pan/tilt head further comprises a second pantograph linkage disposedon a side of the mounting platform opposite that of the first pantographlinkage.
 3. The pan/tilt head as set forth in claim 1, wherein thecenter of gravity is spatially offset from the mounting platform.
 4. Thepan/tilt head as set forth in claim 1, wherein the first pantographlinkage is defined by parallel members connected with the mountingplatform and transverse members transverse to and connected with theparallel members.
 5. The pan/tilt head as set forth in claim 4, furthercomprising a tilt motor operatively coupled with at least one of thetransverse members to selectively tilt the mounting platform withoutmoving the center of gravity.
 6. The pan/tilt head as set forth in claim1, further comprising: a tilt drive train operatively coupling a tiltmotor and the pantograph linkage to selectively tilt the mountingplatform without moving the center of gravity; and an independent pandrive train operatively coupling a pan motor and the mounting platformindependently from the tilt motor to selectively pan the mountingplatform without panning the tilt drive motor.
 7. The pan/tilt head asset forth in claim 1, further comprising: a pan drive train including atleast a hollow pan drive shaft, the pan drive train coupling a pan motorand the mounting platform; and a tilt drive train including at least atilt drive shaft disposed within the hollow pan drive shaft, the tiltdrive train coupling a tilt motor and the pantograph linkage.
 8. Thepan/tilt head as set forth in claim 7, wherein the tilt drive shaft, thehollow pan drive shaft, the tilt drive motor, and the pan drive motorare arranged concentrically along an axis that passes through the centerof gravity.